This invention relates to antiperspirant stick compositions of the so-called dry-feeling type comprising an emulsion of an aqueous solution of an astringent in a solid matrix comprising a volatile, water-insoluble liquid and having stability relative to separation in the molten state and stability relative to leaking in the solid state.
Antiperspirant compositions are well known in the cosmetic art. These compositions are formulated as aerosols, gels, sticks, creams, pump sprays and lotions and comprise an astringent, typically comprising one or more zirconium salts and/or aluminum salts, in various forms such as a dry, impalpable powder, an alcohol solution or an aqueous solution. Of these various forms of astringents the aqueous solution is known to be the most effective antiperspirant.
However, an antiperspirant composition having water as the continuous phase, such as an aqueous solution of an astringent, or an oil-in-water type emulsion thereof, is less desirable than a composition comprising a dry powder or an alcohol solution thereof because it tends to feel wet when applied to the human skin and to go through a tacky state during the drying period after application.
Gee et al., U.S. Pat. No. 4,122,029 have disclosed water-in-oil type compositions having broad utility and comprising a polydiorganosiloxane-polyoxyalkylene copolymer and a water-in-oil type surfactant. When formulated as an antiperspirant emulsion of an aqueous solution of an astringent, such as aluminum chlorhydrate, emulsified in a volatile, non-aqueous continuous phase the compositions of Gee et al. have a desirable dry feeling when applied to the human skin and do not exhibit the wet-and-tacky effect noted above.
Keil, in a U.S. Patent Application entitled "Antiperspirant Emulsion Compositions", filed on even date herewith and assigned to the assignee of this application, discloses new antiperspirant compositions which have improved efficacy compared to the antiperspirants of Gee et al. and still do not exhibit the wet-and-tacky effect.
Although water-in-oil type antiperspirant compositions such as those of Gee et al. and of Keil, may be formulated in several forms, such as lotions, gels and sprays using well-known methods, the preparation of stick-forming compositions therefrom which do not separate in the molten state and which solidify to a non-leaking stick has not been entirely successful using the conventional teachings of the art.
Cosmetic sticks, such as antiperspirant sticks, are typically prepared by first preparing a molten, solidifiable composition comprising all components and thereafter casting the molten composition in the desired shape and/or dispenser. When the molten composition is an emulsion successful completion of this process requires that the emulsion be stable against separation. In addition, the resulting stick must not leak, i.e. lose liquid. The usual mixing of singular gelling agents with the compositions of Gee et al. and of Keil do not satisfy these requirements.